Making soft tissue and toweling products which promote comfortable cleaning without performance impairing sacrifices has long been the goal of the engineers and scientists who are devoted to research into improving tissue paper. There have been numerous attempts to reduce the abrasive effect, i.e., improve the softness of tissue products. One area which has received a considerable amount of attention is the addition of chemical softening agents (also referred to herein as “chemical softeners”) to tissue and toweling products.
The field of work in the prior art pertaining to chemical softeners has taken two paths. The first path is characterized by the addition of softeners to the tissue paper web during its formation, either by adding a softening ingredient to the vats of pulp which will ultimately be formed into a tissue paper web, to the pulp slurry as it approaches a paper making machine, or to the wet web as it resides on a Fourdrinier cloth or dryer cloth on a paper making machine. See U.S. Pat. No. 5,264,082, issued to Phan and Trokhan on Nov. 23, 1993, and U.S. Pat. No. 5,059,282, issued to Ampulski, et. al. on Oct. 22, 1991.
The second path is categorized by the addition of chemical softeners to tissue paper web after the web is dried or overdried. Applicable processes can be incorporated into the paper making operation as, for example, by spraying onto the dry web before it is wound into a roll of paper. Exemplary art from this field includes U.S. Pat. No. 5,215,626, issued to Ampulski, et. al. on Jun. 1, 1993; U.S. Pat. No. 5,246,545, issued to Ampulski, et. al. on Sep. 21, 1993; U.S. Pat. No. 5,525,345, issued to Warner, et. al. on Jun. 11, 1996, U.S. Pat. No. 6,162,329, issued to Vinson on Dec. 19, 2000, U.S. Pat. No. 6,179,691, issued to Ficke et al. on Jan. 30, 2001; U.S. Pat. No. 6,261,580, issued to Trokhan et al. on Jul. 17, 2001; U.S. Pat. No. 6,420,013, issued to Vinson et al. on Jul. 16, 2002, PCT Applications WO 00/22231 and 00/22233, filed in the name of Vinson et al., published on Apr. 20, 2000; and PCT Application WO 02/48458, filed in the name of Vinson et al., published on Jun. 20, 2002.
Those skilled in the art will recognize that both technology paths, more particularly the second path, are advanced by inventions of chemical softening mixtures having liposomal microstructures present at high concentrations in a vehicle. The most recent of the development work in this area has focused on the improvement of the rheological properties of the chemical softening compositions. U.S. Pat. No. 6,162,329 teaches the use of high concentration compositions of softening agents that maintain a viscosity at a level where they can be easily applied to the web. Specifically, U.S. Pat. No. 6,162,329 teaches the addition of electrolytes to the composition. PCT Applications WO 00/22231 and WO 00/22233 further improve the rheology properties of the high concentration compositions by utilizing a bilayer disrupter to create a micellular structure which allows for more efficient application of the chemical softener to the paper web.
PCT Application WO 02/48458 discloses the use of a preferred combination of a quaternary ammonium softening active ingredient, an electrolyte, a bilayer disrupter and a high molecular weight polymer as a softening composition that reduces spray fracture upon spraying. Example 1 of WO 02/48458 depicts a chemical softening composition containing polyacrylamide, where the polyacrylamide is added directly to the water. The compositions therein may comprise from about 0.01 to about 5% by weight.
Unfortunately, these compositions, when they are sprayed onto the paper product, experience inconsistent spray performance where the level of spray fracture reduction is, at times, insufficient to continuously spray effectively. Without being limited by theory, it is believed that the addition of high molecular weight polymers in their natural form, generally a powder, results in a very slow hydration of the polymer from its coiled solid state to a fully expanded, hydrated state. As a result, depending on how long after mixing and the storage conditions of the mixture, the polymer will have different states when used in the production operation, yielding inconsistent performance characteristics.
Further, in many cases it is impossible to pre-disperse the high molecular weight polymer in the vehicle in an attempt to achieve the fully expanded conformation. Often, the dilution levels required to obtain a dispersion of expanded conformation polymer are so low that when even a small amount of high molecular weight polymer is needed to adjust the rheology of the oil-in-water emulsion to improve sprayability, too much vehicle is delivered to the emulsion thereby undesirably changing the characteristics of the final oil-in-water emulsion. If in response to this, it is attempted to pre-disperse the polymer in a higher concentration dilution, the polymer does not achieve the fully expanded or relaxed conformation needed for optimal rheology control.
Accordingly, it is desirable to find a way to further improve the rheology control of oil-in-water emulsions, to be able to provide a more stable composition which consistently results in reduced spray fracture. Such improved products, compositions, and processes are provided by the present invention as is shown in the following disclosure.